QJEEM20Ph13ce: JEE Main 2020 Physics - Class 11 JEEM20Ph13ce Solution: Two particles of equal mass m have respective initial…

Question

Verified Solution • 2025–26 Session moderate

Two particles of equal mass m have respective
initial velocities

u\widehat i

and

u\left( {{{\widehat i + \widehat j} \over 2}} \right)

.
They collide completely inelastically. The energy lost in the process is :

Accepted Answer

\overrightarrow {{P_i}} = \overrightarrow {{P_f}}

\Rightarrow

mu

\widehat i

+ m

\left( {{u \over 2}\widehat i + {u \over 2}\widehat j} \right)

= 2m

\overrightarrow v

Compare both side

\overrightarrow v =

{{3u} \over 4}\widehat i + {u \over 4}\widehat j

\Rightarrow

{\left| {\overrightarrow v } \right|^2}

=

{{10{u^2}} \over {16}}

\Delta

KE = KE_f – KE_i

=

{1 \over 2}2m \times {{10{u^2}} \over {16}}

-

{1 \over 2}m{u^2}

-

{1 \over 2}m{\left( {{u \over {\sqrt 2 }}} \right)^2}

=

- {1 \over 8}m{u^2}

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